Electric music instrument



March 11,A 1941. R, s. GILBERT ELECTRIC MUSIC INSTRUMENT Filed Sept. 6, i938 4 Sheets-Sheet l TT M w. Y i

INVENTOR. 'E/yr /PH/f/r 6, BY

ATTORNEY.

March 1l, 1941. R. s. GILBERT ELECTRIC MUSIC INSTRUMENT Filed sept. e, 1938 4 sheets-sheet 2 March 11, 1941. R s, GILBERT 2,234,490

ELECTRIC MUSIC INSTRUMENT Filed Sept. 6, 1938 4 Sl'leeLs-Shee 5 @raaf/Y @asf/w ATTORNEY.

March'll, 1941. R, s GILBERT 2,234,490 A I I ELECTRIC MUSIC INSTRUMENT l Filed Sept. 6, 1938 4 Sheets-Sheet 4 ...ZLw

. INVENTOR. /M-zaE/Y 6"/4 aff?? Patented Mar. 11, 1941 UNITED STATES PATENT OFFICE ELECTRIC MUSIC INSTRUMENT Reuben S. Gilbert, Denver, Colo., assigner of fifty per cent to II. W. Michalke, and fifty per cent to Gretchen Anderson Mi Colo.

chalke, both ol Denver,

Application September 6, 1938, Serial No. 228,468 1 Claim. (Cl. 84-1.15)

3 and an electric speaker and are selected by means of a manual key board and manually operated selectors.

The principal object of the invention is to provide an instrument of this character which will be exceedingly simple in its construction; which will avoid the usual thumping or harsh starting and stopping of the tones usually encountered in an electric musical instrument;

which will provide a wide selection of tonal qualities from a single chromatic set of generators; which will produce a'tone volume having a soft acceleration and a gradual deceleration similar to the tones of the usual pipe organ; and in which all rotating tone generators, rotating shafts, gears, and other mechanically driven elements will be eliminated.

Another object of the invention is to provide a tremulant for a musical instrument of this character which will control an over-riding vol- 3 ume on the sound wave which will not interfere with nor interrupt any of the tones or overtones; and to provide a selector system by means of which any over-tones or harmonics, and the volume of loudness thereof, can be selected and controlled as desired without affecting the volume or quality of the remaining tones.

Other objects and advantages reside in the detail construction of the invention. which is v designed for simplicity, economy. and eiiiciency.

4 tion of a tone generator box of the type employed in the improved electrical musical instrument. This section is taken on the line I-I, Fig. 2.

Fig. 2 is a cross section through the tone generator box taken on the line 22, Fig. 1.

Fig. 3 is a fragmentary rear elevation of the tone generator box.

Fig. 4 is a detail section through a key board or manual of the instrument.

Fig. 5 is a plan view of a portion of the key board.

Fig. 6 is a detail view illustrating a suggested construction for the selector switches.

Fig. 7 is a detail section through one of the reed throats of the tone generator.

Fig. 8 is a detail view illustrating the tremulant circuit breaker.

Fig. 9 is a general circuit diagram of the instrument illustrating the selector circuits and a single set of key circuits.

Figs. 10, 11 are charts illustrating to which generator each key of the keyboard is connected.

Basically, this instrument is a. reed instrument; that is, the basic tones are obtained from the vibration of a reed under the influence of an air current. The final tone qualities, however, are infinite in number and are not limlted to, nor need they resemble, the tone quality usually known as a reed tone. The reeds are simply employed as the vibrating armatures of electrical generators. A single chromatic set of reeds is employed. The set may be of any desired length, preferably 85 reeds are employed.

The reeds, indicated at I0, may be of any suitable material. Brass reeds have been found to be highly satisfactory although steel reeds or even wooden reeds may be employed. If nonmagnetic reeds are used a small armature block Il of magnetic iron is secured to the reed, preferably at the point of greatest magnitude of vibration. If iron or steel reeds are used, the 31 magnetic block Il is not necessary.

Each reed is mounted over an orifice I3 in a reed plate I4. The reed plate may be of any desired non-magnetic 'material or may be of wood. An aluminum plate is preferred, however, as it is non-magnetic and is unaifected by humidity. The plate I4 is mounted in an air tight generator box l5 and acts to divide the box into a generator compartment and a vacuum. compartment. During the operation of the instrument, air is continuously exhausted from the vacuum compartment through a suction pipe i6 and suction fan ll. The fan Il is driven from any suitable motor i8. The air is exhausted from the fan through a pressure pipe I9 to the generator chamber on the opposite side of the plate Il so that the air ilows continuously through the reed throat frames I2 and continuously vibrates every reed in the instrument during the operation thereof.

'Ihere need be only suiiicient air to gently vibrate the reeds, in fact, in the actual instrument, the vibration is so slight that it is inaudible and since the reeds are entirely enclosed lto in a sound proof box, it is impossible for any of the reed sounds to escape. I

Above each of the reeds is an electric generator coil 20, wrapped on a hardened steel,

magnetized core 2 I. The cores 2| are all mounted in a generator supporting bar 22 extending over all of the reeds. vThe generator supporting bar may be formed of any desired non-magnetic material, preferably brass, and is drilled for the passage of the cores 2l. The latter are positioned over the armature blocks II and may be set for any 'desired spacing from the blocks by means of suitable set screw 23.

It can be readily seen that as the reeds I0 vibrate, they will vibrate the armature blocks I I in proximity to the extremities of the cores 2l, and in the magnetic field thereof. This will generate a small alternating current in each of the coils 20 of a frequency corresponding to the frequency of its reed. Therefore, as long as the instrument is operated, the individual generator coils 20 are generating electricalcurrents corresponding in frequency to the individual reeds of the entire scale of the instrument.

One terminal of each generator coil is grounded to the supporting bar 22. The other terminals of the coils feed'the generated currents through a system of key switches and selector switches to the primary winding of an audio frequency transformer 24. From the transformer, the current returns through the ground of the instrument to the grounded supporting bar 22 thus completing the generator circuits.

The secondary winding of the transformer -24 feeds the combined transformed currents through a volume control rheostat 25, to an audio amplifying set 26 from whence it is impressed upon any suitable audible sound producer, such as the usual radio or phonographic loud speaker 21.

The volume control rheostat is connected with any suitable pedal operated'structure to be actuated by the foot of the musician to control the volume of sound similarly to the usual swell pedal of an organ. The amplifying set may be any of the usual tube circuits such as employed in radio and electrical musical instruments for amplifying electrical currents to an intensity sufficient to operate a loud speaker to the desired volume.

If the current generated by any single generating coil be passed through the amplifying set it would produce a single pure fundamental tone without perceptible over-tones or harmonics, and would not be particularly musical or pleasing to the ear. In this instrument, however, selector switches are provided by means of which currents of various frequencies from other generator coils can be combined with the fundamental tone current and regulated both as to pitch and vvolume to produce a composite tone of any desired tonal quality. The selector switches are in electrical circuit with a series of individual buss bars or wires 29 whichvextend in parallel relation over the rear extremities of the keys, indicated at 30, of the instrument.

The selector switches may be of any construction which will enable each one of the buss wires v29 to be connected to any desired one of a plurality of transformer taps 3I on the primary of the transformer 24. As illustrated, these switches consist of draw bars 32. Each draw bar carries a spring contact brush 33 which, when the bar is actuated, rides over a series of parallel conducting bars 34, each of which is connected to one of the transformer taps 3|. Current is conducted to the draw bar by means of a metal ball 43 which is constantly forced against the draw bar by means of s. plunger 43. A leaf spring 50 urges the plunger against the ball and also carries the current thereto. The ball rides across notches 32 in the draw bar to properly locate the contact brush 33 over the desired bar 34.

The first buss wire 23 of the series is connected to the beginning of the transformer coil and is grounded so that, when each selector switch is in the "shoved in position of Fig. 9, its generator circuit will be grounded.

The generator circuits are completed by means of key switches attached to the keys 30. The key switches may have any desired construction. As illustrated, they consist of a series of seven, perpendicular, resilient, silver spring, contact wires 36 which extend upwardly between the buss Awires 28. As illustrated, the keys are mounted on spring hinges 36 and are supported by spring rods 31. They may, however, be of any of the standard types. When depressed, the keys swing or tilt all of the wires 35 forwardly so that the seven wires will simultaneously and individually contact the adjacent buss wires 29. Each single key wire 35 is individually connected through a exible multiple cable 38 with one of the generating coils 20 through a resistor 39.

Each generating coil is provided with a plurality of the resistors 39, there being one resistor for each key circuit leading to that coil. The wires 35 of the key switches may be connected tothe generators in any desired relation. It has been found, however, that if the first wire is connected to the fundamental generator of that key and the remaining wires are connected to the generators of the partials or harmonics of that fundamental tone, an infinite variety of tonal qualities may be obtained. A typical example of connections for the key C0 (that is, the second octave below middie C or C2) is illustrated in Fig. 9. In this diagram' the iirst contact wire 35 is connected to genv erator C0, the second contact wire to generator C1, the third contact wire to generator G1, the

fourth contact wire to generator C2, the fifthy connected to seven generators, the latter being one-half tone, respectively, higher than those of C0, and so on throughout the entire chromatic scale.

In the chart of Fig. 10, the generators to which the seven key contact switch wires 35.01' each key are connected are designated by the key letter of the generators. It will be noted that under such a system, there will be but a single connection to all of the generators of the iirst octave (C0 to B0) two connections to each of the generators Cl to Fit; three connections to each of the generators Gl to B1: and seven connections to each of the generators throughout the remainder of the scale.

Between each connection and its generator coil, one of the resistors 33 is placed. All of these resistors are .uniform in resistance, for instance, 20 ohms each. When all seven of the contact switch wires leading from a given generator are closed, the full energy of the generator is used. If only one contact Wire is closed l The next key switch "Ct would have its seven contact wires each similarly ance of the resistor 28 is so high (20 ohms) relative to the impedance of the remainder of the circuit that it will determi-ne the amount of current flow in the circuit.

Therefore, even though a plurality of circuits to a single generator are closed at the same time, the current in each circuit will be of substantially the same amplitude as if but one circuit had been closed to that generator. 'Ihe amplitude in each circuit is, of course, variably controllable by means of the draw bar 32 of the selec-tor switch of that circuit, so that the relative volume of the fundamental tone and the harmonic tones can be adjusted at will.

Current is fed to the motor Iii-through power leads 5i across which condensers 52 and 53 are placed to eliminate motor electrical disturbances.

A tremolo effect is produced by a cam 40 (see Fig. 8) driven from the motor I8.v The cam acts to altemately open and close a .pair of contacts 4| i-n a tremolo circuit 54 which includes an independent series of windings 42 in the secondary of the transformer 24. The tremolo circuit may be closed whenever desired by a tremolo switch 43. To eliminate click caused by the breaking of the circuit at the points 4i, two high resistances 44 and 55 and a condenser 45 are bridged across the tremolo circuit. The resistance is variable so that the magnitude of the tremolo effect may be adjusted as desired. The closing of the contacts 4i acts to short circuit the Winding 42 thus temporarily increasing the impedance of the entire transformer and reducing the' total current now .to the amplifying .set 26.

As thus f-ar described, the generators all have their magnet cores over the position of greatest amplitude of the reeds and thetone qualities are produced by combining the currents from the desired generators. It has been found, however, the reeds themselves develop a number of different harmonic tones along their lengths which can be used to advantage if desired. To do this, a series of generators are placed along the length of the reed, as shown in broken line in Fig. 7. Each generator core is placed over the reed at the proper point to pick up the fundamental vibration and 'the vibrations of the desired harmonics of that reed. The series of generators along each reed are then connected to the switch vwires 35 of lthe key 30 controlling that particular reed. This enables the musician to select any of, or any combination of, the harmonics of the reed and to control the volume of each individual harmonic independently, by varying the position of the draw bars 32, so as to produce synthetically any desired tonal quality.

It is preferred in actual construction to group the solenoids and reeds in fifths or in other harmonic relationship to prevent any discordant Vibrations from adjacent reeds or solenoids from being picked up. For yconvenience in description the solenoids have been illustrated and described as in the successive order of' the chromatic scale. Actually, it is preferred to group all of the Cs together, then the D's, the Es, the Fis, etc. Any other adjacently harmonic grouping may be employed.

While a specic form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within .the scope of the appended claim, without departing from the spirit of the invention.

Having thusdescribed the invention, what is claimed and desired secured by Letters Patent is:

An electrical wave form generator for musical instruments comprising an airtight housing, a partition plate mounted horizontally in said housing and dividing the same into an upper pressure chamber and a lower vacuum chamber, said plate having openings formed therethrough arranged in spaced relation to each other longitudinally thereof, reeds carried by said plate and each located over an opening therein, a supporting bar mounted in said housing and extending longitudinally in the upper chamber in vertical spaced relation to the plate and the reeds, said bar being formed with bores located over the reeds and the openings in the plate, straight magnetic cores extending through the bores and adjustably secured therein with their lower ends terminating adjacent' the reeds at the point of greatest fundamental vibration,

ing all of the reeds to simultaneously generate currents in all of lthe solenoids.

REUBEN s. GILBERT. 

